Generation III

Giga Drain can now hit a substitute and will properly heal the user when damaging a substitute. When used on a Pokémon with the Liquid Ooze Ability, the user will lose the amount of HP it would have gained instead.

Generation IV

The move's base PP was raised to 10. If the user is holding a Big Root, the HP restored is increased by 30% (making the restored HP 65% of the damage dealt). Big Root does not increase the damage dealt.

Generation V

Giga Drain's base power has been increased from 60 to 75.

Generation VI

Giga Drain cannot be used if the user is under the effects of Heal Block.

In other games

Giga Drain inflicts damage and restores the user's HP based on the damage inflicted. In Gates to Infinity and Pokémon Super Mystery Dungeon, ½ of damage dealt will be restored to the user. In Gates to Infinity, the HP restored will be based off the HP lost by the target, while in Super Mystery Dungeon, the HP restored is based off the overall damage dealt. For example, Giga Drain dealing 120 damage to a target with 50 HP will restore 25 HP in Gates to Infinity, but 60 HP in Super Mystery Dungeon.

In the main series

The three mountains on Torterra's shell glow green, and matching energy beams extend from their tips. The beams wrap around the opponent's body, drain its energy, and then recede back into Torterra's shell when the attack is complete.

Ninjask flies in circles above the opponent for the entire duration of the attack. Its body glows green, leaving behind a turquoise trail of energy that forms a ring. Once the ring is completed, Ninjask's eyes glow red, and green static from the circle hits the opponent, draining its energy and making its body glow green.

Torterra opens its mouth and releases a beam of energy from it at the opponent. When it hits, the beam covers the opponent's body and absorbs its energy. The beam then goes back into Torterra's mouth and is swallowed.